I just downloaded the Ask Toolbar in Google Chrome and it says it can access all the data on my computer. Should I be concerned?

You need not be. This is standard language from Chrome applied to extensions. You can read more about these warnings here.

The Ask Toolbar does not look at any data on your computer other than the files it has installed to enable the product on your device. The toolbar software does not collect personal information of any kind, nor does it monitor or report any of your browsing activity. In short, the goal of Ask Toolbar is to provide a superior search experience on an anonymous basis and without any additional monitoring, contextual ads or other nuisances.